Apparatus for the administration of anaesthetics



June 17, 1958 H. R. MARRETT APPARATUS FOR THE ADMINISTRATION OF ANAESTHETICS Filed July 8, 1955 4 Sheets-Sheet 1 Mmey;

June 17, 1958 H. R. MARRETT 2,839,055

I APPARATUS FOR THE ADMINISTRATION OF ANAESTHETICS Filed July 8, 1955 4 Sheets-Sheet 2 A ttorn e ys June 17, 1958 I H. R. MARRETT APPARATUS FOR THE ADMINISTRATION OF ANAESTHETICS 4 Sheets-Sheet 3 Filed July 8, 195? Q Inventor WWW Attorneys June 17, 1958 H. R. MARRETT 2,339,055

APPARATUS FOR THE ADMINISTRATION ANAESTHETICS Filed July 8, 1955 4 Sheets-Sheet 4 lnuenlor ttorneyf United States Patent? APPARATUS FOR THE ADMINISTRATION OF ANAESTHETICS Henry Rex Marrett, Coventry, England, assignor to Airmed Limited, Harlow, England Application July 8, 1955, Serial No. 520,842 Claims priority, application Great Britain July 16-, 1954 13 Claims. c1. 128-188) This invention relates to apparatus for administering inhalent gas mixtures topatients, more particularly for anaesthetic and analgesic purposes. in standard apparatus of this kind, the patient breathes intoand out of a re-breathing bag, the patients exhalations being passed through an absorber which removes carbon dioxide from them before being fed back to the patient. There are in use today, two systems of routing the gases, one called the To & Fro system and the other called the Circle system. In the To & Fro system, the gases pass through the absorber both on their way to the re-breathing bag and again on their Way back to the patient. In other words, the patient breathes through the absorber both on expiration and on inspiration. In the Circle system, however, the gases pass through the absorber only on their way to the bag, returning to the patient over a circuit which by-passes the absorber. In other words, the patient breathes through the absorber, only on expiration.

The T0 & Fro system provides for a high degree of carbon dioxide absorption but that isaccompanied by a relatively high resistance to breathing. Furthermore, the To & Fro system of operation can result in accumulation of carbon dioxide in the circuit producing what is known as dead space.

On the other hand, the Circle system of operation provides relatively low resistance to breathing and a reduced risk of dead space but does not provide for a very high degree of carbon dioxide absorption. .=In the apparatus in accordance with the invention provision is made for both To & Pro and Circle operation and each kind of operation can be selected at will. 'Normally, apparatus for administering anaesthetics is designed either for the To & Fro system or for the Circle system. If, during a surgical operation, it is found desirable to change from one system to the other, for example, where it is found that the patient is too weak to overcome the resistance in the To & Fro circuit, the supply must be switched from one apparatus to another. According to the invention an apparatus for administering anaesthetics comprising a re-breathing bag and a carbon dioxide absorber, is provided with valve-controlled passages interconnecting the bag, the absorber and the patients inspiratory and expiratory conduits such that a circuit can be established from the expiratory conduit to the inspiratory conduit through the absorber and the bag for Circle operation or an alternative circuit can be established from one conduit to the other through the absorber, the bag and the absorber for To & Fro operation, the change from one circuit to the other being efiected without any interruption in the supply to the patient. I

In the preferred form of the invention, a single valve is provided for switching over from one kind of operation to the other. A single valve has important advantages over a number of valves. It avoids cumbersome complications in design of the apparatus but, more im- 2,839,055 Patented June 17, 1958 ICE portant, it simplifies the task of the anaesthetist who, it will be understood, may have to effect theswitch as a matter of emergency. A single valve will necessarily be of somewhat complicated structure but that is of no great consequence as long as it lends itself to simple actuation. The simplest form of actuation is rotation and the preferred form of valve in accordance with the invention is therefore a rotary valve.

An example of portable apparatus in accordance with the invention embodying a rotary valve, is shown in the accompanying drawings in which:

Figure 1 is a perspective view of the apparatus;

Figure 2 is a plan of Figure 1;

Figure 3 is an elevation partly in section of the carbon dioxide absorber, the re-breathing bag and the contro valve of the apparatus; I

Figure 4 is a section taken on the line IV-IV in Figure 3 and showing the control valve in the To & Fro position;

Figure 5 is a view similar to that of Figure 4 showing the valve in the Circle position; and

Figure 6 is a section taken on the line VI-VI in Figure '3.

The anaesthetic administering apparatus shown in Figures 1- and 2 comprises a control unit 10, a vaporiser 12 for a gas such as ether and a vaporiser 14 for a second gas such as chloroform or trichlorethylene. The control unit is connected to the vaporisers by conduits 16 and 18 and the vaporisers are connected together by a conduit 20.

The control unit 10 comprises a control valve 22 (see Fig. l), a housing 24 for the control valve, and a carbon dioxide absorber 26 containing a quantity of soda lime 27. A conduit 28, leads from the control valve housing 24 to a re-breathing bag 30. A patients inspiratory conduit 36 is branched oft" the conduit 16and is adapted to be connected to a face-piece or mask (not shown) worn by the patient during an administration. A patients expiratory conduit 38 connected to the valve housing 24 is adapted to be connected also to the facepiece or mask. In the said conduits 36 and 38 there are respectively one-way inspiratory and expiratory valves 32 and 34.

The control unit 10 is shown in greater detail in ure 3.

The valve housing 24 is divided, by a partition 40, into two compartments; an upper compartment 42 and a lower compartment 44. The conduits 16, 18 and 28 are connected to the compartment 42, and the carbon dioxide absorber and the conduit 38 are connected to the compartment 44.

The control valve 22 is adapted to be rotated in the upper compartment 42, and is provided with a control knob 46 for that purpose.

The lower compartment 44 is divided by three radial walls 59, 52 and 54 into three chambers 56, 58 and 60, as shown in Figure 6. The patients expiratory conduit 38 leads to the chamber 56 and chambers 58 and 60 are each connected to the soda lime absorber 26 at such points therein that gas can flow from one chamber to the other only by passing through the soda lime in the absorber. The absorber 26 is in the form of a double Walled canister, having inner and outer containers 86 and '88. The inner container 86 carries the soda lime 27 and the two containers are arranged one inside the other with a space 89 between them. An internally threaded flange 90 depends from the outside of the compartment 42 and direct communication with the chamber 58 of the compartment 44, and the space 89 between the containers ges d as is inrcommuni-cation with the chamber 60 of the" compartment 44, through a slot 92inits outer wall. The'control valve 22 has a peripheral wall 61 and a base 71 (see Fig. 1). As can be seen from Figures 4 .andj, therer areanumber. of;por.ts';62..72tin the .wall61 andtwo portsi74 and 76 inthe base 71; Thespace above Cthefbase bounded by the peripheral .walli-has a dividing ,wall .77 proceeding across it between the ports 74.-and' 76.

The partition 40 has in it three ports78,,.80 and 82 .and is also provided with .a pin 84 which protrudes control valve 22 is limited bythe abutment of one of the bounding edges 73-and 75 againstthe pin.

ethrough .theport 74 so :thatrotationa'l movement of the flhus, rotation .of the valve ;22 between positions'in V which the edges 73 and, 75 ,abut-againstthe pin 8.4.serves to control the various passages interconnecting the bag 30, the absorber '26 and the patients inspiratory and expiratory conduits 136 and 38.so that a circuit can be established from the conduit 38 to the conduit 36 through Due to the position of the ;valve 22 the port 78 in the:

partition 40, is uncovered and the gases pass through that port and through the port 76 in the base 71 of the valve 22 into the space to the left hand side (as viewed in Fig. 4) of the dividing wall '77. The gases, having arrived there, cannot pass round the circuit through the vaporisers, as the one-way :valve 32 .is closed and thus provides a dead end. Thus, the gases pass again through .t-he port 76, downwards in Figure 3, and through the .port' 80 in the partition 40 into the chamber 58 of the compartment 44 (see Fig. 6). V

As the chamber 58 leads to the soda lime in the absorber 26, the gases pass through the soda lime in the direction of the dotted arrow A, and along the space 89 between the containers 86 and 88 and in the direction of the dotted arrows B, through the slot 92 into the chant.- ber 60 of the compartment 44. The chamber 60 has an outlet in the shape of the port 82 in the partitionAt), thus the gases pass through that port, which, due to the position of the valve 22 is uncovered, and through the port 74 in the base 71 of the valve 22 into the space to the right hand side of the dividing wall 77 (as viewed in liig. 4). The gases then follow the only path open to them from this space, that is through theport 66 and the conduit 28 into the bag 30.

As the patient inhales' with the valve 22 in the Toand Fro position of Figure 4, the gases take the same path as just described, but in reverse, until they arrive for the second time in the space to the left-hand side of the dividing wall 77. From this space they cannot take their original path through the ports 76 and 78 into the chamber 56, because the one-way valve 34 is closed and thus provides a dead end. Instead, the gases are drawn by the patient out of the compartment 42, through the port 72, along the conduit 18, through the vaporisers 14 and 12 and travel back to the patient by Way of conduits 16' and 38 and the one-way valve 32.

In Figure 5, the valve 22 is shown in the position it occupies for the Circle kind ofoperation.

As the patient exhales, gases pass through the one-way valve 34 and the conduit 38 into the chamber 56 (Fig. 6). Due to the position of the valve 22, the port 78 in the partition is uncovered and the gases pass through that port, and through the port 76 in the base 71 of the valve 22 into the space to the left-hand side (as viewed in Fig. 5) of the dividing wall'77. From this space there i on on at repeate the gases an tha ..is back through the port 76' in the valve base 71, through the port 80 in the partition 46 and into the chamber 58 (Fig. 6).

As the chamber 58 leads to the soda lime in the absorber '26, the gases passthrough the soda lime in the I direction of the dotted arrow A, and along the space 89 between the containers 86 and 88 and inthedirection of the dotted arrows B, through thetslot 92 into the chamber 680i the compartment; Thechamherhas an outlet in the shape of the portj82 in the p'artition 40, thus the gases pass through that port, which due to the position of the valve ;22,is uncovered, and through the port 74in the base 71 of the valve 22 into the space to the right hand sideofthe dividing wall 77 (as viewedin Fig. 5). The gases theujollow theonly path open to them from this space, that is through the port66 and the conduit 28 into the bag 30..

In Figure 5, the valve 22 has' been turned anticlockwise about 45 outofits position 'inyFigure 4 and the conduit 18 is, therefore, in communication with the space to 'the right of the dividing wall '77 through the port 70'. Thus,

as the patient inhales in :the Circle position, the gases .leave the :bag '30, pass through the port -66 .and thecon- .duit28 into' the ;space.to the right of the wal177; The

gases cannot pass back through the ports 74' and 82 as the one-.way.valve 34-.is closedand thus provides a'deadend, so theyare drawn by the patient through the'-port :70 along the conduit 18, through the vaporisers-14 and 12 andtheconduits 20 and 16 and travel backIo-the patient byway of conduit 38 and the one-way valve 32.

The vaporisers 12 and 14 are in the form of'bottles containing fgas in liquid form. They are providedwith control knobs 13 and '15 'by means of which vapour inlet valves (not shown) can be operated to allow vapourto find its way into the apparatus through the conduits*16,=18 and 20. With both knobs 13 and 15 in the Ofi position, a circuit is established from the conduit 16 to the conduit 18, passing through the vaporisers but by-passing -.the contents of the bottles. I

It is essential that :when -trichloroethylene is bein g admi-nstered, it should not'come into contact with'the soda lime in the absorber. 'If' this should be allowed to happen, a toxic gas would result, which would be injurious to'the patient. 'The controlvalve provides the necessary insurancetagainst such a state of affairs occurring.

Thus, by turning the control valve 22 approximately 45 in an anti-clockwise sense out of its position as shown in Figure 5, acircuit is established which enables the patient to .breath' intoand out of the bag 30, throughthe inspiratory and expiratory conduits 36 and 38, without the gases passing through the 'absorber26. Only with the valve 22 in this so-called locking position, can trichloroethylene be introduced into the apparatus atall. In all other positions of the valve 22,-a safety locking deviceis efiective toprevent the knob 15, which liberates the trichloroethylene vapour, from being operated.

The locking device comprises a spring loaded pin 96 (see Fig. 1) which is axially movable in a tube 98 lying between the vaporiser 14 and the housing 24 of the control unit 10. With the control knob 15 in the off position a cam detent is brought opposite the vaporiser end of the pin 96 which being spring loaded is urged into the detent so that its control unit end lies flush with the inner surface of the housing24. In this position of the pin 96, the

control valve'knob 46 can bernanipulated into and out of its various positions. However, unless the control valve 22is in the locking position any attempt to-move the knob. 15. will not succeed because the pin 96 will be prevented from moving axially by that part of the peripheral wall 61 which is continuous and which lies beneath the ports, 62-72.

"Ihere is however, an aperture which when the control,

valve is in the locking position, and only then, lies opposite the pin 96' at the control unit end thereof. Thus,

assaults inthat position with the absorber 26 out of circuit, the knob 15 can be turned, the pin riding out of the detent and entering the aperture, to adminster trichloroethylene to the patient.

Having turned the knob 15 and caused the pin 96 to enter the aperture in the wall 61 the valve 22 itself is locked against movement. Thus, while trichloroethylene is being adminstered to the patient it is impossible to bring the absorber into circuit. The risk of toxic gases being generated is thereby eliminated.

Besides the supply of gas in vapour form from the vaporisers, other gases, such as oxygen or nitrous oxide can be supplied by way of a pipe 100 through flow-meters 101, 102, 103 and 104. s

It will be seen that the control valve which forms a part of the apparatus in accordance with the invention, provides a very simple means of control, and in particular enables the anaesthetist to switch over from the To and Fra to the Circle system, or vice versa, by simple turning movement. It also eliminates the danger of trichloroethylene being passed through the absorber.

I claim: l

1. In apparatus for administering inhalent gas mixtures, having a carbon dioxide absorber, a re-breathing bag and patients inspiratory and expiratory conduits, a rotary valve controlling the flow of gas between the patients inspiratory and expiratory conduits, a housing for said valve, a partition in said housing dividing it into upper and lower compartments, ports in said partition, passages connecting said upper compartment to said patients inspiratory conduit and to said bag, passages connecting said lower compartment to said patients expiratory conduit and to said carbon dioxide absorber, said rotary valve having a base and a peripheral wall, ports in said base adapted to'be brought into and out of communication with said ports in said partition by rotation of said valve and ports in said peripheral wall adapted to be brought into and out of communication with said passages connecting said upper compartment to said patients inspiratory conduit and to said bag by rotation of said valve.

2. In apparatus for administering inhalent gas mixtures having a carbon dioxide absorber, a re-breathing bag and patients inspiratory and expiratory conduits, a rotary valve having two positions and controlling the flow of gas. between the patients said inspiratory and expiratory con duits, a housing for said valve, a partition in said housing dividing it into upper and lower compartments, ports in said partition, passages connecting said upper compartment to said patients inspiratory conduit and to said bag, passages connecting said lower compartment to said patients expiratory conduit and to said carbon dioxide absorber, said rotary valve having a base and a peripheral wall, ports in said base adapted to be brought into and out of communication with said ports in said partition, and ports in said peripheral wall, adapted to be brought into and out of communication with said passages connecting said upper compartment to said patients inspiratory conduit and to said bag by rotating said valve between said two positions, in one of which positions a circuit is established on expiration by the patient from said patients expiratory conduit through one of said ports in of said ports in said base, another of said ports in said partition, said absorber, another of the ports in said base, one of said ports in said peripheral wall and said passage leading to said bag, and on inspiration by the patient, from said bag through said passage, said port in said peripheral Wall, another port in said peripheral wall and a passage leading to said patients inspiratory conduit.

3. in apparatus for administering inhalent gas mixtures as claimed in claim 2 having at least one vaporiser for a gas to be administered, a passage leading direct from a port in said peripheral wall and constituting part of the circuit established with said rotary control valve in said first position, and another passage leading from a port in said peripheral wall to said patients inspiratory conduit via said vaporiser and constituting part of the circuit established with said rotary control valve in sai other position. i l

4. Apparatus for administering inhalent gas mixtures comprising an inlet for gas to be administered, a carsaid partition, one of said ports in said base, another of a said ports in said partition, said absorber, a third port in said partition, another port in said base, a port in said peripheral wall, and a passage leading to said bag, and on inspiration by the patient, from said bag through said passage, said port in said peripheral wall, said other port in said base, said third port in said partition, said absorber, said other port in said partition, said first port in said base and another port in said peripheral wall to a passage leading to said patients inspiratory conduit and in the other of which positions a circuit is established, on expiration by the patient, from said patients expiratory conduit through one of said ports in said partition, one

'bon dioxide absorber, a re-breathing bag, a patients in.- spiratory conduit, a patients expiratory conduit, a oneway valve in each of said conduits, passages connecting said gas inlet to said inspiratory conduit and connecting said conduits to said absorber and said bag and a control valve having two positions, in one of whicha circuit is established from said expiratory conduit to said inspiratory conduit via said absorber, said bag and said absorber again in that order, and in the other of which ,a circuit is established from said expiratory conduit to said inspiratory conduit via said absorber and said bag, without a second passage through said absorber;

5. Apparatus as claimed in claim 4 in which the control valve is a rotary valve.

6. Apparatus for administering inhalent gas mixtures, comprising an inlet for gas to be administered,a carbon dioxide absorber, a rte-breathing bag, a patients inspiratory conduit, a patients expiratory conduit, a one-way valve in each of said conduits, passages connecting said gas inlet to said inspiratory conduit and connecting said conduits to said absorber and said bag and a control valve having two positions, in one of which a circuit is established from said expiratory conduit to said inspiratory conduit via said absorber, said bag and said absorber again in that order, and in the other of which a circuit is established from said expiratory conduit to said inspiratory conduit via said absorber and said bag in that order Without a second passage through said absorber.

7. Apparatus for administering inhalent gas mixtures comprising an inlet for gas to be administered, a carbon dioxide absorber, a re-breathing bag, a patients inspiratory conduit, a patients expiratory conduit, a one-way valve in each of said conduits, passages connecting said gas inlet to said inspiratory conduit and connecting said conduits to said absorber and said bag, and a control valve having three positions, in one of which a circuit is established from said expiratory conduit to said inspiratory conduit via said absorber, said bag and said absorber again in that order, in another of which a circuit is established from said expiratory conduit to said inspiratory conduit via said absorber and said bag without a second passage through said absorber, and in a third of which a circuit is established from said expiratory conduit to said inspiratory conduit via said bag.

8. Apparatus as claimed in claim 7 in which said second mentioned circuit is established from said expiratory conduit to the said inspiratory conduit via said absorber and said bag in that order.

9. Apparatus as claimed in claim 8 in which said second mentioned circuit is established from said expiratory conduit to said inspiratory conduit via said bag and said absorber in that order.

10. Apparatus for administering inhalent gas mixtures comprising an inlet for gas to be administered, a carbon ,dioxide absorber, a rebreathing bag, a patients inspiratory conduit, a patients expiratory conduit, a one-way valve in each of'said conduits, passages connecting said gas inlet to said inspiratory conduit and connecting said conduits to said absorber and said bag, a vaporiser and meansfor establishing a circuit from said vap'oriser to conduit via said absorber and said bag without a second passage through said absorber, and in. a third of which a circuit is established from said expiratory conduit to said inspiratoryv conduit via said bag and means operative to preventestablishment of said circuit from said vaporiser to the patients inspiratory conduit while the said control valve is out of said third position.

7 11. Apparatus for administering inhalent gas mixtures comprising a carbon dioxide absorber, a reebreathingbag, a' patients inspiratory conduit, a patients expiratory conduit, a'one-way valve in each of said conduits, a vaporiser for a gas to be administered, passages connecting said vaporiser to said inspiratory conduit and connecting said conduits to said absorber and said bag, a vapour inlet valve in the passage between said vaporiser and said patients inspiratory conduit, and a control valve having three positions, in one of which a circuit is established from said expiratory conduit to said inspiratory conduit via said absorber, said bag, and said absorber "again in that order, in another of which a circuit is established from said expiratory conduit to said inspiratory conduit via said absorber and said bag without a second passage through said absorber, and a third of which a circuit is established from said expiratory conduit to said inspiratoiy conduit via said bag, a cam movable with said vapour inlet valve, an aperture in said control valve, and a pin to fit said aperture adapted 12. Apparatus as claimed in claim 11 in which the said control and vapour inlet valves are both rotary valves. 13. Apparatus for administering inhalent gas mixtures comprising an inlet for gas from an external source, a

carbon'dioxide absorber, a re-breathing bagyapaticnts.

' inspiratory conduit, a patients expiratory conduit, a'

conduit to said inspiratory conduit via said bag, and

one-way valve in each of said conduits, passages connecting said'gas inlet to said inspiratory conduit and connecting 'said conduits to said absorber and Said bag a V 7 pair of vaporisers connected to said inspiratory conduit, a vapour inlet valve between each of the vaporisers and the, patients inspiratory conduit, a rotary control valve having three positionsin one of which acircuit is established from said expiratory conduit to said inspiratory conduit via saidabsorber, said bag, and said absorber again in that order, .in another'of which a circuit is established from said expiratory conduit to'sai d inspiratory conduit via said absorber and said bag with out a second passage through said absorber, and in a thirdof which a circuit is established from said expiratory meansassociated with the said rotary control valve and one of said vapour inlet valves to prevent a circuit being;

established, through that vapour inlet valve from the vaporiser which it control to the said patients inspiratory conduit, while the said control valve is out of the 'sai d third position. 7

2,407,221 Bloomheart Sept. 10,1946

Marrett Feb. 19, 1952 

